Changes for 3.0 release. (dotnet#240)

Adding in-app documentation for the ui command (dotnet#225)

* Adding in-app documentation for the ui command

* Update src/Microsoft.HttpRepl/Resources/Strings.resx

Co-Authored-By: Scott Addie <10702007+scottaddie@users.noreply.github.com>

* Update src/Microsoft.HttpRepl/Resources/Strings.resx

Co-Authored-By: Scott Addie <10702007+scottaddie@users.noreply.github.com>

Renaming assembly from dotnet-httprepl to httprepl (dotnet#223)

Set the temp file extension based on the content type (dotnet#208)

* Set the temp file extension based on the content type

* Making RealFileSystem public so we can remove an IVT; adding another content type for json

* Modifying RealFileSystem's GetTempFileName implementation to always require an extension; pass in .tmp if we can't find a more appropriate one. Also moved a couple integration tests to be unit tests now that there was no file system dependency.

* Fixing a namespace and making a public class internal again

* Changing RealFileSystem to disallow period-only extensions. Adding tests for the failure conditions, renaming the success conditions

Initial implementation of the connect command, with tests (dotnet#179)

* Initial implementation of the connect command, with tests

* Removing the auto-detect features of the set base command

* Remove the set swagger command and refactor the connect command a bit to make it reusable by the other commands that need part of it (list, help, all the http commands, etc).

Merge pull request dotnet#105 from aspnet/dev/jodavis/packagemetadata

Add a PackageIconUrl for the Nuget package